Topband: WD-1A 2-way Beverage

[RA6LBS]

Lee, sorry for the late reply, I've been traveling.

>>And RF signals from Back direction of reception is not "injected" at
>>feed point, so direct multiplication of attenuation by length does not play here.

> It  seems to me that All the signals from the back ( two transformer
> receiver  end)  direction  come  from the reflection transformer and
> therefore travel the full length of the transmission line

Indeed,  the  signals reflected FROM the reflection transformer (
that`s the single transformer end ) is traveling along the
transmission line and DECREASED by its attenuation.

BUT! how and where from, those signals (which we call reverse direction
signals) are created? As I sad, "injected" from "nowhere" at two
transformers end (via transformer?) and coming along the same
transmission line (with its attenuation 
again) in the direction of a reflection transformers?
To be twice the lines length attenuated in the last?

NO.

This is a common mistake I can hear often and my point was to clear it.
Sorry if I didnt made it clear in the first post.

Simplifying a lot, the wire is "illuminated" by radio waves from reverse
direction at its length and that means that some "drops" of a signal
is coming along its full length and some of them not the full one
before they reach the reflection transformer!

And that`s  the only way explaining LESS, not the "double" (lines length
* db/ft *  2)  attenuation  I  can  observe  here at my QTH and in a
number of installation and reports from other users of this type of
antenna.

Of course that observation are not on a 1db accuracy. But its quite
obvious and repeatable, that the reverse direction signals are less
then twice the line`s length attenuation down.

> At times here in the early a.m. this antenna drops clear into the
> noise floor of the receiver and its low noise
> preamp.

Your are lucky one! my noise level from Hydro Power Station (less then
5 km away in a US direction) and a Nuclear Power station (less then
20 km away in JA direction) is around S4 at BEST times ... and the
city by it self ...

One can make ANY, even PERFECT directional antenna but if its
direction is to the noise SOURCE, than its usefulness is limited by
the noise source level only ...

> It  seems  to  me  you  cannot verify that your antenna is above the
> noise  floor  just  by  connecting  it to the RX with all the losses
> involved.

But in assumption that there is no common mode ingress what else can
increase the matched input RX noise? And if the noise did increased,
if its sounds as  a normal band noise from that direction (and it is
different at different times of the day and directions!) at that time
and carrying also some signals sky waves propagated?

>  I still wonder about the incorrect termination effects due to
> losses and its affect on the RDF/pattern.

I have no hope that someone will repeat last century work
by Litva and others investigating the Beverage antenna with
helicopters for real life pattern measurements.

The A/B test I have made here, at moderate length up to 700 feet
clearly shows for me they are the same.

Much more disturbing factors are local noise and common mode problems.


-- 
Andrey
RA6LBS/AB2ZB                          mailto:ra6lbs at volgodonsk.ru
                                 
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